New Energy Storage Using Co₃O₄ Electrode Materials Preparation And Performance Study

To meet the increasing demands for energy conversion/storage systems and environmental protection, the development of new-generation energy storage devices is still of great importance. Supercapacitors come into view of more and more researchers by virtue of its many advantages, such as high power density, environmental friendliness, long lifespan, high efficiency, and many other advantages. As the key component of supercapacitor, the structure and properties of electrode material have a vital influence on the performance of the supercapacitor. Thus, it is critical to design a smart architecture, in which the electroactive materials are efficiently utilized, and a fast electron transport and ion diffusion can be guaranteed.In this work, we take anode material of supercapacitor as the object of the research. Specifically, we prepared Co3O4 nanowire arrays(NWAs) on conductive nickel foam through a combination of hydrothermal method and annealing treatment. The effect of annealing temperature on the capacitance of material was investigated. We test and analyze the material through cyclic voltammetry and galvanostatic charge/discharge and electrochemical impedance spectroscopy electrochemical methods and reach a decision that Co3O4 NWAs electrode has a maximum capacitance at an annealing temperature of 300 °C. The specific capacitance is calculated to be 1147 F/g at the current density of 1 A/g. To further investigate their morphologies, the samples were subjected to SEM and TEM measurement, and the images show that the Co3O4 NWAs vertically grow on Ni substrate and tend to be interconnected with each other, forming a porous struture. This would greatly facilitate the electron transports and diffusion of the electrolyte ions within the electrode. In order to further improve the energy storage capacity of the supercapacitor, this work has carried on the design of a new structure of electrode, in which a layer of NiMoO4 ultrathin nanosheets was coated on the surface of Co3O4 NWAs, obtaining a three-dimensional Co3O4@NiMoO4 hierarchical nanowire arrays structure. The ultrathin NiMoO4 nanosheets were uniformly dispersed on the surface of Co3O4 nanowires without destroying the original arrayed structure. Electrochemical performance tests show that the specific capacitances of material are significantly increased after the integration of secondary structure, and a higher specific capacitance(1607 F/g) is obtained at current density of 1 A/g. In summary, we can conclude that the adoption of NiMoO4 ultrathin nanosheets secondary structure not only improves the mass loading of active material, but also greatly improve the utilization efficiency and specific surface area of active material, thus providing more active sites during the electrochemical reaction process. This study can serve as a reference for researching capacitance properties of Co3O4 NWAs as well as secondary structure.